PolyGerrit: Add next/previous page key bindings to keyboard shortcuts

Shortcuts for next/previous page navigation were added in: I0f8c4f55.
Mention them on the keyboard shortcuts overlay to reflect this.  Given
that the next/previous page keys only exposed on change list view, but
not on dashboad view, split the table bodies for keyboard shortcuts for
this views.

Test Plan:

* Open change list view
* Type: ?
* Keyboard shortcuts overlay is opened
* Verify, that the name is: "Change List" and that this lines appear:
  "n or ] Go to next page"
  "p or [ Go to previous page"

* Log in
* Open dashboard
* Type: ?
* Keyboard shortcuts overlay is opened
* Verify, that the name is: "Dashboard" and that the keyboard shortcuts
  for next/previous page not rendered

Bug: Issue 4259
Change-Id: I3c82ddad3a21e1f88d4ea6c396095c2e6fea0b34

polygerrit-ui/app/elements/core/gr-keyboard-shortcuts-dialog/gr-keyboard-shortcuts-dialog.html

@@ -134,8 +134,8 @@ limitations under the License.
       </table>
 
       <table>
-        <!-- Change List and Dashboard -->
-        <tbody hidden$="[[!_computeInChangeListView(view)]]" hidden>
+        <!-- Change List -->
+        <tbody hidden$="[[!_computeInView(view, 'gr-change-list-view')]]" hidden>
           <tr>
             <td></td><td class="header">Change list</td>
           </tr>
@@ -147,6 +147,35 @@ limitations under the License.
             <td><span class="key">k</span></td>
             <td>Show previous change</td>
           </tr>
+          <tr>
+            <td><span class="key">n</span> or <span class="key">]</span></td>
+            <td>Go to next page</td>
+          </tr>
+          <tr>
+            <td><span class="key">p</span> or <span class="key">[</span></td>
+            <td>Go to previous page</td>
+          </tr>
+          <tr>
+            <td>
+              <span class="key">Enter</span> or
+              <span class="key">o</span>
+            </td>
+            <td>Show selected change</td>
+          </tr>
+        </tbody>
+        <!-- Dashboard -->
+        <tbody hidden$="[[!_computeInView(view, 'gr-dashboard-view')]]" hidden>
+          <tr>
+            <td></td><td class="header">Dashboard</td>
+          </tr>
+          <tr>
+            <td><span class="key">j</span></td>
+            <td>Select next change</td>
+          </tr>
+          <tr>
+            <td><span class="key">k</span></td>
+            <td>Show previous change</td>
+          </tr>
           <tr>
             <td>
               <span class="key">Enter</span> or

polygerrit-ui/app/elements/core/gr-keyboard-shortcuts-dialog/gr-keyboard-shortcuts-dialog.js

@@ -35,11 +35,6 @@
       return view === currentView;
     },
 
-    _computeInChangeListView: function(currentView) {
-      return currentView === 'gr-change-list-view' ||
-          currentView === 'gr-dashboard-view';
-    },
-
     _handleCloseTap: function(e) {
       e.preventDefault();
       this.fire('close', null, {bubbles: false});